Advanced retroreflecting aerial displays

ABSTRACT

A persistent image retroreflecting display that enables the formation of a real image in free space includes a first light source that generates a polarized light output; a retroreflector module adjacent a first side of the first light source; a quarter waveplate coupled to the retroreflector module and adjacent the first light source; and a reflective polarizer positioned between the first light source and a viewer of the display.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the following: U.S. ProvisionalApplication Ser. No. 62/442,695, filed on 5 Jan. 2017; U.S. ProvisionalApplication Ser. No. 62/470,710, filed on 13 Mar. 2017; U.S. ProvisionalApplication Ser. No. 62/507,032, filed on 16 May 2017; and U.S.Provisional Application Ser. No. 62/529,342, filed on 6 Jul. 2017; allof which are incorporated in their entireties by this reference.

TECHNICAL FIELD

This invention relates generally to the image display field, and morespecifically to new and useful advanced retroreflecting displays.

BACKGROUND

Image displays are an integral part of modern life. From televisions tomonitors to smartphone and tablet screens, image displays provide userswith the ability to view and interact with information presented in avariety of forms.

The advent of three-dimensional displays has enabled users to experienceimages with higher realism than would be possible with theirtwo-dimensional counterparts; however, the vast majority of 3D displaysrequire the use of a head-mounted display (HMD) or other cumbersomeperipheral.

Free-space 3D displays remove the need for an HMD, allowing multipleusers to see and manipulate content in a shared experience.Unfortunately, the few existing free-space 3D displays are hampered by anumber of issues, including size, limited view angle, low resolution andbrightness, scene distortion, and high cost. Thus, there exists a needin the image display field to create new and useful advancedretroreflecting aerial displays. This invention provides such new anduseful displays.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram view of a system of a preferred embodiment;

FIG. 2 is a diagram view of a first configuration of a system of apreferred embodiment;

FIG. 3 is a diagram view of a second configuration of a system of apreferred embodiment;

FIG. 4 is a diagram view of a system of a preferred embodimentillustrating the plane of convergence;

FIG. 5 is a diagram view of a system of a preferred embodimentillustrating multiple planes of convergence;

FIG. 6A is a diagram view of a system of a preferred embodiment withlight sources in series;

FIG. 6B is a diagram view of a system of a preferred embodiment withlight sources in parallel;

FIG. 6C is a diagram view of a system of a preferred embodiment withmultiple light sources and beam splitter modules;

FIG. 7 is a diagram view of a system of a preferred embodimentillustrating correlation between light source placement and imageposition;

FIG. 8A is a diagram view of a retroreflector module of a system of apreferred embodiment;

FIG. 8B is a diagram view of a retroreflector module of a system of apreferred embodiment;

FIG. 8C is a diagram view of a retroreflector module of a system of apreferred embodiment;

FIG. 9 is a diagram view of a retroreflector module of a system of apreferred embodiment;

FIG. 10 is a diagram view of a system of a preferred embodiment having ahigh-index material in the display light path;

FIG. 11 is a diagram view of a system of a preferred embodiment;

FIG. 12 is a diagram view of a system of a preferred embodiment;

FIG. 13 is a diagram view of an assistant display of a system of apreferred embodiment;

FIG. 14 is a diagram view of a system of a preferred embodiment;

FIG. 15 is a diagram view of a system of a preferred embodiment;

FIG. 16 is a diagram view of a system of a preferred embodiment;

FIG. 17A is a diagram view of a system of a preferred embodiment;

FIG. 17B is a diagram view of a system of a preferred embodimentillustrating light paths;

FIG. 18A is a front view of a system of a preferred embodiment;

FIG. 18B is a front view of a system of a preferred embodiment;

FIG. 18C is a top-down view of a system of a preferred embodimentillustrating light paths;

FIG. 18D is a top-down view of a system of a preferred embodimentillustrating light paths;

FIG. 18E is a top-down view of a system of a preferred embodimentillustrating light paths;

FIG. 19 is a diagram view of a system of a preferred embodiment;

FIG. 20 is a diagram view of angle-dependent views produced by a systemof a preferred embodiment;

FIG. 21 is a diagram view of a light source and d lens of a system of apreferred embodiment;

FIG. 22A is an example view of a first view of a three-dimensionalimage;

FIG. 22B is an example view of a second view of a three-dimensionalimage;

FIG. 23 is a diagram view of a system of a preferred embodiment; and

FIG. 24 is a diagram view of a system of a preferred embodiment.

DESCRIPTION OF THE INVENTION EMBODIMENTS

The following description of the invention embodiments of the inventionis not intended to limit the invention to these invention embodiments,but rather to enable any person skilled in the art to make and use thisinvention.

1. High-resolution Retroreflecting Aerial Display

A high resolution retroreflecting aerial display 100 includes a lightsource 110, a beam splitter module 120, and a retroreflector module 130,as shown in FIG. 1. The display 100 may additionally or alternativelyinclude an assistant display 140, an onboard computer 150 and/or acontextual lighting system 160.

As shown in FIG. 2, the retroreflecting aerial display 100 functions toenable viewers to see two- and/or three-dimensional image data frommultiple perspectives at the same time. The light source 110 preferablygenerates light (i.e., a light output) based on image data transmittedto or generated by the display 100. The output of the light source 110is projected or otherwise transmitted to the beam splitter module 120;at the beam splitter module 120, the light is split into transmitted andreflected components. In a first configuration, as shown in FIG. 2, thetransmitted light impinges upon the retroreflector module 130 and isreflected back to the beam splitter module 120, where it is again splitinto transmitted and reflected components; then, the reflected componentis directed to the display area. In this configuration, the light source110 is opposite the retroreflector module 130. In a secondconfiguration, as shown in FIG. 3, the reflected light impinges upon theretroreflector module 130 and is reflected back to the beam splittermodule 120, where it is again split into transmitted and reflectedcomponents; then, the transmitted component is directed to the displayarea. In this configuration, the retroreflector module 130 is preferablyoriented at ninety degrees relative to the light source 110(alternatively, the retroreflector module 130 may be oriented at anyangle relative to the light source 110; e.g., as shown in FIG. 10). Ineither of these configurations, the retroreflector module 130 preferablyenables the light emitted by the light source 110 to converge in theviewing area, as shown in FIG. 4. Note that, as shown in FIG. 4,convergence may be in free space; alternatively, convergence may bewithin any optical material (e.g., a lens or display volume).

If the display 100 includes an onboard computer 150, the onboardcomputer 150 may convert or aid in converting image data transmitted tothe display 100 into an ideal format for projection by the light source110. Additionally or alternatively, computers external to the system 100may be used to perform part or all of image processing.

The light source 110 functions to generate images (i.e., light generatedfrom image data) for display by the retroreflecting aerial display 100.The light source 110 is preferably a planar two-dimensional displaycomprising a set of individually addressable pixels, but mayadditionally or alternatively be any suitable display. For example, thelight source 110 may comprise one or more movable light sources; e.g., alaser that may be scanned across a set of positions to simulate theappearance of multiple light sources (i.e., display multiplexing).

The light source 110 is preferably an RGB color light source (e.g., eachpixel includes red, green, and blue subpixels) but may additionally oralternatively be a substantially monochromatic light source or any otherlight source (e.g., a white light source).

The light source 110 is preferably a projector or projector light engine(e.g., DLP, laser, LCoS, and/or LCD projector) but may additionally oralternatively be any suitable display (e.g., an LCD monitor/TV display,an OLED display, an e-ink display, an LED array, a spinning LED display,an e-ink display, an electroluminescent display, a neon display, etc.).In one variation of a preferred embodiment, the light source 110includes a liquid crystal panel with a collimated backlight.

In another variation of a preferred embodiment, the light source 110 isa volumetric display; for example, the volumetric display of U.S. patentapplication Ser. No. 15/266,027, filed 15 Sep. 2016, the entirety ofwhich is incorporated by this reference. Use of a volumetric display orother three-dimensional display as the light source 110 may enable thedisplay 100 to display real-space 3D images; e.g., as shown in FIG. 5.In the example as shown in FIG. 5, a two-layer (L1, L2) volumetricdisplay is used as the light source 110, resulting in a two-layerthree-dimensional image. The light source 110 may be any type ofvolumetric display; e.g., oscillating volumetric displays, stacked LCDpanels, and/or stacked transparent OLED panels, in addition to thelight-folding volumetric display described above.

The retroreflecting aerial display 100 preferably includes a singlelight source 110, but may additionally or alternatively include multiplelight sources 110. For example, multiple light sources 110 may be placedin series and/or in parallel as shown in FIG. 6A and FIG. 6Brespectively. As another example, multiple light sources 110 may be usedwith multiple beam splitter modules 120, as shown in FIG. 6C. Note thatany combination of light sources 110, beam splitter modules 120,retroreflector modules 130, and/or additional optics (e.g., mirrors,lenses, etc.) maybe used in the retroreflecting aerial display 100. Inconfigurations utilizing multiple light sources 110, the light sources110 may be offset, angled, rotating, curved, or otherwise configuredsuch that the image created by each light source is offset in depth(similar to with volumetric displays); e.g., as shown in FIG. 7.

The example as shown in FIG. 7 shows that the position and orientationof the light source 110 may affect the position and orientation of thedisplayed aerial plane. While this effect may be harnessed in a staticconfiguration, the display 100 may additionally or alternatively includemechanisms (e.g., motors, piezoelectronics, etc.) for moving one or moreparts of the display 100 to change the position and/or orientation ofthe displayed aerial plane. In particular, the display 100 may beconfigured to rapidly modify this displayed aerial plane position, saidmodification synchronized with image data displayed by the light source110 (e.g., by the onboard computer 150 or otherwise) to produce a 3Dimage. More specifically, the display 100 may display a first 2D image,corresponding to a first ‘depth slice’ of a 3D image, at a first aerialplane distance, and then a second 2D image, corresponding to a second‘depth slice’ of a 3D image, at a second aerial plane distance (and soon, if there are more than two slices). This 3D multiplexing techniquemay be produced by using multiple light sources 110, by moving lightsources 110, by moving beam splitter modules 120, by tuning optics ofthe display 100, or using any technique. For example, a movingtwo-dimensional display may display, at a first time and position, afirst two-dimensional image, and, at a second time and position, asecond two-dimensional image; the first and second positions separatedby a non-zero distance; resulting in perception of a 3D image when themovement is fast enough (e.g., oscillation frequency of more than 30 Hz)

The light source 110 may include optical elements (e.g., lenses,mirrors, waveguides) that function to couple light into the beamsplitter module 120 and/or the retroreflector module 130. For example,the light source 110 may include a mirror positioned at 45 degreesrelative to the light source 110 output (resulting in a 90-degreeredirection of light source output). As another example, the lightsource 110 may include a collimating lens designed to increasecollimating of the light source 110 output. As a third example, thelight source 110 may include a lens designed to scale (or otherwisedistort) light source 110 output (e.g., reduce in size or increase insize). Such a lens may scale light source 110 output uniformly (e.g., 2×decrease in both image dimensions) or non-uniformly (e.g., no decreasein first image dimension, 4× decrease in other image dimension). As afourth example, the light source 110 may include a lens that manipulatesthe focal plane of the viewed image; such a lens may be tunable(allowing depth of field to be swept). If such a lens were tunable at ahigh rate, this may provide an expanded perceived depth of field to aviewer.

The light source 110 may additionally or alternatively include anypassive or active optical elements to prepare light for use by thedisplay 100 for any other purpose. For example, the light source 110 mayinclude filters or splitters. As another example, the light source 110may include microlens arrays and/or Fresnel lenses substantially similarto those of the retroreflector module 130 (see that section for moredetail).

The beam splitter module 120 functions to direct light from the lightsource 110 to the retroreflector module 130 and to viewers of thedisplay 100. The beam splitter module 120 preferably includes ahalf-silvered mirror beamsplitter, but may additionally or alternativelyinclude any suitable type of beamsplitter (e.g., glass prism based,dichroic optical coating based, dichroic mirrored prism, etc.). The beamsplitter module 120 preferably transmits and reflects equal power (50%),but may additionally or alternatively have any transmission/reflectioncoefficients. For polarizing beamsplitters (or in general),beamsplitting may be a function of light source polarization. Similar tothe light source 110, the beam splitter module 120 may additionally oralternatively include any passive or active optical elements to preparelight for use by the display 100 for any other purpose. For example, thebeam splitter module 120 may include lenses, polarizers, filters, and/orsplitters. As another example, the beam splitter module 120 may includemicrolens arrays and/or Fresnel lenses substantially similar to those ofthe retroreflector module 130 (see that section for more detail).

As shown in FIG. 8A, the retroreflector module 130 includes one or moreretroreflectors 131. The retroreflector module 130 may additionally oralternatively include microlens arrays 132 and/or Fresnel lenses 133.The retroreflector module 130 functions to reflect light (e.g., from thelight source 110 or beam splitter module 120) impinging upon theretroreflector module 130 at an angle substantially similar to the angleof incidence, thus considerably reducing scattering compared to a planarmirror.

The retroreflectors 131 may be any type of retroreflectors, includingcat's eye retroreflectors, corner retroreflectors, and/orphase-conjugate mirror retroreflectors.

Cat's eye retroreflectors may be any type of retroreflector including arefracting optical element and a reflective surface. Typical cat's eyeretroreflectors are spherical; additionally or alternatively, cat's eyeretroreflectors may include a normal lens focused onto a curved mirror.In one example implementation, the retroreflectors 131 are part of amicrosphere or microprismatic retroreflective film. Such a film ispreferably fabricated by microsphere deposition, but may additionally befabricated using any additive (e.g. deposition, plating) or subtractivetechniques (e.g., milling, etching), but may additionally oralternatively be fabricated by any suitable means.

Corner retroreflectors feature a set of three mutually perpendicularreflective surfaces; in some cases, corner retroreflectors may be formedby three flat mirrors bracketing an air space; in others, cornerretroreflectors may be formed by the surfaces of a solid object (e.g., aglass cube). In one example implementation, the retroreflectors 131 arepart of a dihedral corner reflecting array (DCRA). In this exampleimplementation, the DCRA preferably comprises a two-dimensional array ofdihedral corner reflecting elements positioned such that incident lightis able to reflect twice inside the reflecting elements, resulting inthe light traveling along a path plane-symmetric to incident path. TheDCRA is preferably fabricated by milling, etching, or otherwise creatingan array of square through holes in a highly reflective substrate orfilm (e.g., a metal), but may additionally or alternatively befabricated by any suitable means.

The retroreflector module 130 is preferably aligned with the lightsource 110 and/or beam splitter module 120 such that the majority oflight incident on the module 130 is accepted by the module 130 (that is,the angle of the light with respect to the retroreflectors 131 is suchthat the light contributes to the formation of a plane-symmetric realimage). Additionally or alternatively, optics (e.g., lenses, mirrors,etc.) may be used in the light path in between the retroreflector moduleand the light source 110 and/or beam splitter module 120 to improve orotherwise modify acceptance of light incident on the retroreflectormodule 130.

In one implementation of a preferred embodiment, the retroreflectormodule 130 includes a microlens array 132, as shown in FIG. 8A. Themicrolens array 132 functions to focus light on the retroreflectors 131.While the use of the microlens array 132 may improve focusing ability,in some cases, the microlens array 132 may introduce visual artifactsthat affect the focal locking of the viewers on the aerial imagery(e.g., if the lenses are not small enough). In such a case, the display100 may include mechanisms (e.g., motors, piezoelectronics) forvibrating and/or rotating the microlens array 132 relative to the beamsplitter module 120.

In a variation of this implementation, the microlens array 132 mayinclude structures (e.g., optical fibers, polarizing films, opaquesegments, reflective planes etc.) that block errant reflections (e.g.,those with angle substantially different than incident angle on theretroreflectors 131), as shown in FIG. 8B and FIG. 8C. As shown in FIG.8B, these structures may be integrated with the microlens array 132 ormay be independent as shown in FIG. 8C. These structures may be, forinstance, perpendicular to the retroreflector module 130.

The retroreflector module 130 may additionally or alternatively includeone or more Fresnel lenses 133, as shown in FIG. 9, as a replacementand/or supplement for the microlens array 132. The use of Fresnel lenses(e.g., a Fresnel lens stack) may provide advantages over the microlensarray 132 (e.g., less distortion).

The retroreflector module 130 may additionally or alternatively includeany other optical elements (e.g., mirrors, lenses, waveguides, filters,polarizers) or other light-altering treatments (e.g., anti-glare surfacetreatments or layers, viewing angle restriction treatments or layers).

In one implementation of a preferred embodiment, a material with arefractive index greater than 1 is placed between the beam splittermodule 120 and the viewer, as shown in FIG. 10. This serves to reducethe size of the display 100 without overly reducing the size of theprojected image. The material is preferably a transparent glass orpolymer, but may be of any opacity and/or any material. The material ispreferably prism-shaped, but may additionally or alternatively be anyshape or structure.

In another implementation of a preferred embodiment, the display 100 mayinclude optical elements that reduce glare/ambient light and/or increaseviewing brightness of the display 100. For example, as shown in FIG. 11,the retroreflector module 130 may include a quarter waveplate; while thebeam splitter module 120 may include a polarizing beam splitter stack(e.g., reflective polarizer, quarter waveplate, linear polarizer, andfinally anti-reflective coating). As a second example, as shown in FIG.12, the beam splitter module 120 may include a (standard,non-polarizing) beamsplitter, a linear polarizer, a second beamsplitter,a quarter waveplate, a linear polarizer, and finally anti-reflectivecoating. The display 100 may additionally or alternatively include anysuitable optical elements to reduce glare, increase contrast, increasebrightness, and/or in any other way modify the display 100.

The assistant display 140 functions to augment the display capabilitiesof the display 100 by providing a display (preferably transparent orsemi-transparent) in or near the free-space image produced by thedisplay 100. An example configuration of the display 100 featuring anassistant display 140 is as shown in FIG. 13.

The assistant display 140 is preferably transparent, semi-transparent orwith tunable transparency, but may additionally or alternatively be ofany opacity. The assistant display 140 is preferably a LCD or OLEDpanel, but may additionally or alternatively be any display as describedin the section regarding the light source 110.

The display 100 (e.g., via the onboard computer 150) may strategicallyuse the assistant display 140; for example, the assistant display 140may be used to display text or labels relating to a 3D video, while therest of the 3D video is projected into real space via the display 100.

Similar to the light source 110, the display 100 may include a pluralityof assistant displays 140, arranged or configured in any manner.

The onboard computer 150 functions to perform image processing for imagedata received by the display 100 prior to display by the light source110. For example, the onboard computer may separate 3D model informationinto slices to be projected by the light source 110. The onboardcomputer 150 may additionally or alternatively function to prepare 3Dimage data for voxel representation in any manner. For example, if lightfolding is performed by the display 100 (i.e., images are sliced andanisotropically scaled), the onboard computer 150 may performinterpolation between pixel values to determine a new transformed pixelvalue. As another example, the onboard computer 150 may performdithering to simulate blurring at image edges. As a third example, theonboard computer may send control commands (e.g., activatingpiezoelectric movement of a beam splitter module 120).

If the display 100 includes a volumetric display, the onboard computer150 may control image preparation for the volumetric display (asdescribed in U.S. patent application Ser. No. 15/266,027).

The onboard computer 150 may additionally or alternatively function tocontrol general properties of the light source 110, the beam splittermodule 120, the retroreflector module 130, the assistant display 140,and/or the contextual lighting system 160; for example, the onboardcomputer 150 may control brightness of light source 110 pixels tosimulate changes of opacity in a displayed image.

Note that the functions described as performed by the onboard computer150 may additionally or alternatively be performed by any other computersystem (e.g., a distributed computing system in the cloud).

In one implementation of an invention embodiment, the onboard computer150 is communicative with another electronic device (e.g., a smartphone,a tablet, a laptop computer, a desktop computer, etc.) over a wiredand/or wireless communication connection. In this implementation, datamay be streamed or otherwise communicated between the onboard computer150 and the other electronic device. For example, a smartphone maytransmit video information to the onboard computer, where it is slicedinto depth slices by the onboard computer 150. Additionally oralternatively, depth slicing may be performed by the other electronicdevice. In general, the task of image processing may be performed and/orsplit between any number of electronic devices communicative with theonboard computer 150.

The contextual lighting system 160 functions to light the periphery ofthe display 100 (or nearby area) with a light meant to match or resemblelighting conditions programmed into digital imagery displayed by thedisplay 100. By doing so, the contextual lighting system 160 can ‘lock’the imagery in the real world for some users; for example, a user's handmay be lit to match the lighting of a particular part of a digital scenenear the user's hand. This may substantially increase immersiveness.

The contextual lighting system 160 may control lighting properties(e.g., color, duration, intensity, direction, degree of focus,collimation, etc.) based on explicit instructions in the digitalimagery. Additionally or alternatively, the contextual lighting system160 may control lighting properties in any manner. For example, thecontextual lighting system 160 may (for digital images without explicitcontextual lighting instructions) average the color across a subset ofan image and light the display 100 with this light.

The contextual lighting system 160 may include any number and/or type oflighting devices; for example, color controllable LEDs.

The contextual lighting system 160 is preferably controlled by theonboard computer iso, but may additionally or alternatively becontrolled by any controller or computer system.

The display 100 may also include means for interaction tracking. Forexample, the display 100 may include a depth camera that tracks userinteraction with the display 100, allowing control and/or manipulationof the image displayed based on hand gestures and/or other interactionbetween a viewer and the display 100 as measured by the depth camera. Asanother example, the display 100 may include a transparent touch sensorthat tracks viewer touch interactions on surfaces of the display 100.

In one implementation of a preferred embodiment, the display 100includes an ultrasonic haptic feedback module and a head tracker (e.g.,a camera or other device that tracks head position, orientation, and/ormotion). In this implementation, tactile feedback via the hapticfeedback module maybe modified according to head tracking data (or otherdata, e.g., hand tracking data, body tracking data, video/audio capturedata, etc.). Tactile feedback may also be provided by haptic gloves thatare coordinated through the onboard computer 150 to provided tactilefeedback that is coincident with the visual feedback of the system.

In another implementation of a preferred embodiment, the display 100includes an infrared-opaque wand for interaction with aerial display(e.g., the wand is air gap or water containing, or of an IR blocking butvisible-light transparent plastic or glass). This wand functions as aninteraction instrument (in addition to a user's bare hands) that can beread by a depth camera, but which does not block the light of the aerialimage like a visible-light interaction instrument or a hand would, inthe case of interaction that extends past the plane of the aerial image.Additionally or alternatively, the wand may feature an infraredreflector and/or light emitter to better enable tracking.

Tracking and interaction are preferably controlled by the onboardcomputer 150, but may additionally or alternatively be controlled by anycontroller or computer system.

2. Flat Retroreflecting Aerial Display

A flat retroreflecting aerial display 200 includes a light source 210and a retroreflector module 220, as shown in FIG. 14. The flatretroreflecting aerial display is a retroreflecting aerial displaysubstantially similar to an embodiment of the display 100, with aretroreflector module 220 that is at least partially transparent ortranslucent. Accordingly, the light from the light source 210(substantially similar to the light source 110, though preferablypolarized) may pass through the back of the retroreflector module 220,then through a quarter waveplate, optional optics (e.g., a Fresnel lensstack or microlens array), before being reflected by a reflectivepolarizer 230 (similar to a beamsplitter module 120 oriented at a 0degree angle to the light source; alternatively, a polarization filterif the light source 110 polarization and the reflective polarizerpolarization are members of the same polarization basis set). After thereflection, the light again passes through the quarter waveplate, isretro-reflected, passes through the quarter waveplate again, and finallypasses through the reflective polarizer, forming a real image in freespace. This process is pictured in more detail as shown in FIG. 15. Forexample, if the light source 210 is linearly polarized (withpolarization L1), the quarter waveplate may convert the light to acircular polarization (C1). The reflective polarizer (which reflectspolarization C1 and transmits orthogonal circular polarization C2)reflects the C1 polarized light. As a result of the reflection, thislight is incident upon the quarter waveplate again as C2 polarizedlight, so the quarter waveplate converts this to L2 linear polarizedlight (L2 being orthogonal to L1). After retroreflection, the light isagain incident on the quarter waveplate, and is converted back from L2polarized light to C2 polarized light. Finally, the light is incident onthe reflective polarizer, which it now passes through, forming the realimage in free space.

In a variation of an invention embodiment, the retroreflector module 220is dynamically reconfigurable (e.g., electrically, mechanically, etc.).In this variation, reflection and/or transmission properties of theretroreflector module 220 are spatially configurable to modify theoutput image of the display 200.

The display 200 may additionally or alternatively include assistantdisplays, onboard computers and/or contextual lighting systems similarto those described for the display 100.

3. Dual-perspective Flat Retroreflecting Aerial Display

A dual-perspective flat retroreflecting aerial display Soo includes alight source 310, a retroreflector module 320, and a reflectivepolarizer 330, as shown in FIG. 16. The dual-perspective flatretroreflecting aerial display is a retroreflecting aerial displaysubstantially similar to the display 200, except that the retroreflectormodule 320 is not necessarily translucent/transparent, and the lightsource 310 is positioned in front of the retroreflector module 320,rather than behind it.

In the display 300, the light source 310 is preferably substantiallysimilar to the light source 110, except that the light source 310 emitspolarized (which is possible, but not necessary, for the light source110). This can be accomplished either by an already polarized lightsource (e.g., an LCD) or the use of additional polarization filters.

Enabled by the display 300, each viewer on opposite sides of the display300 can see a different image if the light source 110 projects twodifferent images (such as the front of a person on one side of thedevice and the back of a person on the other side), as shown in in FIG.16.

The quarter waveplate and reflective polarizer in the display 300prevent the viewer from seeing the original screens under the reflectivepolarizer (which, given the polarized light source 110, serves as abeamsplitter), essentially only allowing the aerial image to be seen.This blocking function can also be accomplished to some extent withmicrolouver privacy filters on the light source 310 (or in any othermanner).

Note that while the light source 310 is shown at a 90 degree angle tothe retroreflector module 320 in FIG. 16, the angle between the lightsource and retroreflector module 320 may be any suitable angle(s).

The display 300 may additionally or alternatively include assistantdisplays, onboard computers and/or contextual lighting systems similarto those described for the display 100.

The display 300 may additionally or alternatively be constructed with anon-polarizing beamsplitter in place of the reflective polarizer 330,similar to the display 100 (in which case the light source 310 need notnecessarily be polarized).

4. Thin Scattering-Retroreflecting Aerial Display

A thin scattering-retroreflecting aerial display 400 includes a lightsource 410, a retroreflector module 420, a scattering module 430, and areflective polarizer 440, as shown in FIG. 17A. The thinscattering-retroreflecting aerial display 400 is a retroreflectingaerial display substantially similar to a variation of the display 100that utilizes a polarized light source 410 (similar to the light source110); further, the reflective polarizer 440 in the display 400 ideallyacts as a polarization filter rather than a beamsplitter (e.g., similarto the reflective polarizer of the flat retroreflecting aerial display200). Finally, the thin scattering-retroreflecting aerial display 400utilizes the scattering module 430 to reproject the output of the lightsource within the optical path of the retroreflector module 420 (similarto the retroreflector module 120) and reflective polarizer 440 toachieve an effect similar to that of the flat aerial display 200 withoutrequiring a translucent or transparent retroreflector module 420. Inthis manner, the thin scattering-retroreflecting aerial display 400 isable to be thinner than traditional aerial displays—for example, thedistance from the scattering module 430 to the retroreflector 420 may beapproximately the same distance as the ‘float distance’ (the distancefrom the scattering module 430 to the image plane).

In the display 400, polarized light from the light source 410 (e.g., ashort-throw projector) is incident upon the scattering module 430. Thescattering module 430 preferably scatters the incident lightperpendicular to the plane of the scattering module 430 (i.e., towardthe reflective polarizer 440); alternatively the scattering module 430may scatter light in any direction. After being scattered by thescattering module 430, the light incident on the reflective polarizer440 is preferably transmitted by the polarizer 440 toward the quarterwaveplate and retroreflector module 420. After passing through thequarter waveplate, being reflected by the retroreflector module 420, andagain passing through the quarter waveplate, the light is rejected(i.e., reflected) by the reflective polarizer due to changedpolarization, and passes through the quarter waveplate, is reflected bythe retroreflector module 420, and passed again through the quarterwaveplate. After this second pass, the light is transmitted by thereflective polarizer 440, passes through the scattering module 430, andforms a real image outside the scattering module 420. For example, asshown in FIG. 17B, if the light source 410 is linearly polarized (withpolarization L1), the reflective polarizer 440 transmits the L1 light.In the first trip to the retroreflector module 420, the L1 light isconverted by the quarter waveplate to a circular polarization (C1).After retroreflection, the light is reflected as C2 polarized light(orthogonal to C1). The quarter waveplate then converts the C2 polarizedlight to L2 light (orthogonal to L1), which is reflected by reflectivepolarizer 440. In the second trip to the retroreflector module 420, thelight is converted from L2 to C2 to C1 to L1 by a process similar tothat in the first pass (quarter waveplate to retroreflector to quarterwaveplate). Finally, this light is transmitted by the reflectivepolarizer 440 and then by the scattering module 430. Note thatsuccessful implementation of this technique depends upon the scatteringmodule 430 scattering the originally incident light more strongly thanthe twice-retroreflected light. The scattering module 430 is discussedin more detail in the following section.

The scattering module 430 functions to scatter light emitted by thelight source 410 within the optical path of the retroreflector module420. As previously described, the scattering module 430 preferablyscatters originally incident light (input light) more strongly thanlight emerging from the reflective polarizer 440. The scattering modulemay comprise any material or structure with this result. For example,the scattering module 430 may comprise a translucent scattering foilthat exhibits this property. As another example, the scattering module430 may comprise metallic nanoparticles embedded in a transparentsubstrate. As a third example, the scattering module may comprise angledmicrolouvers.

The scattering module 430 may scatter light differently based on anylight property. For example, the scattering module 430 may more stronglyscatter light with higher intensity, or with larger angles of incidence(for the configurations as shown in FIG. 17A and 17B, both of thesewould result in the intended effect). Alternatively, the scatteringmodule 430 may scatter light dynamically based on any light property(e.g., angle of incidence, wavelength, power, polarization, etc.).

In a variation of an invention embodiment, a component of the display400 exhibits dynamic polarization properties. For example, the lightsource 410 may dynamically change polarization, resulting in two imagedepths (a real image at the image plane when the polarizer 440 isaligned in polarization with the light, a virtual image behind thepolarizer 440 when not aligned in polarization with the light). Thescattering module 430 may dynamically alter light polarization for asimilar effect.

In another variation of an invention embodiment, the scattering module430 has dynamically configurable scattering properties. For example, thescattering module 430 may change from translucent (as shown in FIG. 17B)to opaque, also resulting in two image depths (again, the real image atthe image plane when translucent, and a real image projected on thescattering module surface when opaque).

The display 400 may additionally or alternatively include assistantdisplays, onboard computers and/or contextual lighting systems similarto those described for the display 100.

The display 400 may additionally or alternatively be constructed with anon-polarizing beamsplitter in place of the reflective polarizer 440,similar to the display 100 (in which case the light source 410 need notnecessarily be polarized).

5. Persistent Image Retroreflecting Aerial Display

A persistent image retroreflecting aerial display 500 includes a movinglight source 510 (similar to the light source 110), a retroreflectormodule 520 (similar to the retroreflector module 120) and a reflectivepolarizer 530, as shown in FIGS. 18A, 18B 18C, and 18D. In the display500, the light source 510 forms an image by rotating or oscillatingperpendicular to an optical axis of the light source 510. For example,the light source 510 may comprise a strip of LEDs (overlaid with apolarizing filter) that oscillates side to side, as shown in FIG. 18B orthat performs rotary oscillation around one end (e.g., in apendulum-like fashion), as shown in FIG. 18A. The LEDs are modulated asthe light source 510 moves, creating an image viewable to humans due toimage persistence. Alternatively, the light source 510 may comprise acylinder with columns of LEDs that rotates (creating a similar effect),as shown in FIG. 18D.

In the display 500, the retroreflector module 520 preferably flanks orotherwise extends perpendicular to the direction of viewer at or nearthe light source, as shown in FIG. 18C and 18D. Alternatively, theretroreflector module 520 may be positioned in any manner.

The display 500 creates an image in a manner similar to that of thedisplay 200, except that propagation through the retroreflector moduleis not required (and thus the retroreflector module 520 need not betransparent or translucent). Accordingly, the light from the lightsource 510 (substantially similar to the light source 110, thoughpreferably polarized) is initially reflected by the reflective polarizer530, and then is transmitted via the quarter waveplate, reflected by theretroreflector module 520, transmitted again via the quarter waveplate,and finally transmitted through the reflective polarizer 530, forming animage in free space, as shown in FIG. 18C.

For example, if the light output of the light source 510 has a firstlinear polarization (L1), the light output may be reflected by thereflective polarizer 530 (which rejects L1 but passes orthogonal linearpolarization L2), then pass through the quarter waveplate (whichconverts the light to a first circular polarization C1). Uponretroreflection, the C1 light is reflected as C2 light (orthogonalcircular polarization to C1), which again passes through the quarterwaveplate, converting the light to L2, which then passes through thereflective polarizer 530.

Note that other retroreflective displays of this disclosure may utilizereflective polarizers in a similar manner (as described for the display200).

The display 500 may additionally or alternatively include assistantdisplays, onboard computers and/or contextual lighting systems similarto those described for the display 100.

The display 500 may additionally or alternatively be constructed with anon-polarizing beamsplitter 540 in place of the reflective polarizer530, substantially similar to beam splitting module 120 of the display100 (in which case the light source 510 need not necessarily bepolarized and a quarter waveplate may not be necessary). An example isas shown in FIG. 18E.

6. Superstereoscopic Image Retroreflecting Aerial Display

A superstereoscopic image retroreflecting display 600 includes a lightsource 610, a beam splitter module 620, a retroreflector module 630, anda lenticular lens 640, as shown in FIG. 19.

The display 600 is preferably substantially similar to the display 100,with the addition of the lenticular lens 640. In combination with asuitably configured light source 610 (discussed in later sections), thelenticular lens 640 enables the display 600 to provide angle dependentreal aerial images to viewers. This technique can be used to provideviewers with three-dimensional viewing capability of images on thedisplay; additionally or alternatively, it can be used to provideviewers with different images based on viewing angle relative to thedisplay 600.

For example, as shown in FIG. 20, the display 600 enables differentimages to be viewed at different angles. This effect is enabled by thecombination of the lenticular lens 640 with a light source 610 thatdisplays different pixels (or image segments) based on the positioningof the lenticular lens 640 over the light source 610. For example, asshown in FIG. 21, the image shown to viewers at three angles iscomprised of the pixels labeled 1, 2, and 3, respectively.

Based on the properties of the lenticular lens 640 (e.g., pitch,material, structure, orientation and position relative to the lightsource 610) and desired viewing characteristics (e.g., number ofviewers, view distance, number of views desired, viewing mode, etc.),the display 600 may modify the output of the light source 610 to producea desired result.

In one example embodiment, the number of different views provided by thedisplay 600 is sufficient for superstereoscopic viewing at some viewingdistance; that is, each eye of the viewer receives a different imagefrom the display 600, and as the viewer moves around the display 600,the views change (with the viewing angle). For example, a viewer atangle one may see scene 1 with a right eye and scene 2 with a left eye,where scene 1 and scene 2 create a stereoscopic three-dimensional viewof one or more objects. After the viewer moves from angle one to angletwo, the viewer now sees scene 2 with the right eye and scene 3 with theleft eye, producing a second stereoscopic three-dimensional view of theone or more objects. In this manner, the viewer perceives a threedimensional image (thanks to the stereoscopic effect) at a given viewingangle, and that perception is preserved (thanks to the changing views,which correspond to a rotated view of the one or more objects) as theviewer moves around the display 600, as shown in FIGS. 22A(corresponding to a first view) and FIG. 22B (corresponding to a secondview).

A viewing angle separation (at a given viewing distance) resulting in adifferent image arriving at a viewer's left eye from the image arrivingat a viewer's right eye is henceforth referred to a stereoscopic angle.

The lenticular lens 640 may have any suitable configuration andstructure and may be made of any suitable material. The lenticular lens640 is preferably one-dimensional (e.g., cylindrical lenses arranged incolumns), but may additionally or alternatively be a two-dimensionallenticular lens, fly-eye lens array, or integral imaging lens array.Note that while there is preferably a correlation between addressablesegments (e.g., pixels) of the light source 610 and the lenticular lens640, the lens columns of the lenticular lens 640 need not be at aparticular orientation relative to the light source 610. For example,while columns of the lenticular lens 640 may be aligned with pixelcolumns, they may also be offset at an angle (which allows theresolution loss due to image slicing to be apportioned across both imagepixels columns and rows, rather than only one of these). This techniqueis described further in U.S. Pat. No. 6,064,424. Image slicing ordivision (of light source 610 output) may be accomplished in any mannerto achieve a desired viewing result.

The display 600 may include multiple lenticular lenses 640 and/or otherlenses to produce a desired optical effect. For example, 1D lenticularlenses may be stacked at different orientations to create 2D angularview dependence (thus simulating the effect of a fly-eye lens).

The display 600 may be structured in any of the manners described forthe display 100 (see, for example, FIGS. 6A-6C, FIG. 11, FIG. 12) withthe addition of the lenticular lens 640 between the light source 610 andother components of the display 600.

Similar to the display 100, the display 600 may include any suitableoptical components (e.g., mirrors, lenses, filters, polarizers, etc.).For example, the lenticular lens 640 may include a polarizing laminate(or other polarizer) if the light source 610 is unpolarized (or in anyother scenario), enabling contrast enhancement similar to in the display100.

The display 600 may additionally or alternatively include assistantdisplays, onboard computers and/or contextual lighting systems similarto those described for the display 100.

In one variation of an invention embodiment, the display 600 includes atracking sensor that tracks viewer eye or head motion. In thisembodiment, the display 600 alters output of the light source 610 basedon the position and/or orientation of viewers. For example, while userhead movement (around the display 600) in the horizontal plane may beaccounted for by the superstereoscopic views produced by the display 600(e.g., revolving left resulting in a rotated view of the objectdisplayed by the display 600), vertical movement may not be. In such aninstance, head tracking/eye tracking data may be used to determineviewer vertical orientation relative to the image, and the output of thelight source 210 may be modified in response (e.g., if a viewer movesher head up ten degrees relative to the object, the object viewdisplayed to her is shifted as if the object was a physicalthree-dimensional object). Since individual viewers may only see asubset of stereoscopic views at a given time and position, light source610 output may be modified for only the views seen by a particularviewer (and may be modified differently for views seen by anotherviewer).

Similar to the display 100, the display 600 may incorporate microlensarrays or Fresnel lenses. These optical components may be oriented inany manner with respect to the lenticular lens 640.

As with the display 100, the display 600 may combine its components avariety of configurations; for example, a two-layer superstereoscopicdisplay 600 may incorporate two light sources 610 and two beamsplittingmodules 620 as shown in FIG. 23.

7. Dual-Perspective Flat Superstereoscopic Image Retroreflecting Display

A dual-perspective flat superstereoscopic image retroreflecting display700 includes a light source 710, a retroreflector module 720, areflective polarizer 730, and a lenticular lens 740 as shown in FIG. 24.The display 700 is substantially similar to the display 300, with theaddition of lenticular lenses (as described in the display 600) toproduce multiple views (hence, image sets A and B instead of image A andB) for both viewers A and B. The display 700 may additionally oralternatively include assistant displays, onboard computers and/orcontextual lighting systems similar to those described for the display100.

The display 700 may additionally or alternatively be constructed with anon-polarizing beamsplitter in place of the reflective polarizer 730,similar to the display 100 (in which case the light source 710 need notnecessarily be polarized).

While most of the systems described are presented in their flat andrectangular forms, a number of structural variations that are desirablein certain applications are possible, including curving the sourceimager (for a curved aerial image) or different shapes of the sourceimager (or any other optics of the systems described herein).

As a person skilled in the art will recognize from the previous detaileddescription and from the figures and claims, modifications and changescan be made to the preferred embodiments of the invention withoutdeparting from the scope of this invention defined in the followingclaims.

We claim:
 1. A persistent image retroreflecting display comprising: afirst light source that generates a first light output; wherein thefirst light output has a first linear polarization; a retroreflectormodule adjacent a first side of the first light source; a quarterwaveplate coupled to the retroreflector module and adjacent the firstlight source; and a reflective polarizer positioned between the firstlight source and a viewer of the display; wherein the first light sourcetransmits the first light output to the reflective polarizer; whereinthe reflective initially reflects the first light output to the quarterwaveplate; wherein the quarter waveplate converts the first light outputto a first circular polarization and transmits the first light output tothe retroreflector module; wherein the retroreflector module reflectsthe first light output back to the quarter waveplate, converting thefirst light output to a second circular polarization orthogonal to thefirst circular polarization; wherein the quarter waveplate converts thefirst light output to a second linear polarization orthogonal to thefirst linear polarization; wherein the reflective polarizer transmitsthe first light output and thereafter the first light output convergesto a first visible real image in free space.
 2. The display of claim 1,wherein the first light source, retroreflector module, and quarterwaveplate move in rotary oscillation in a direction perpendicular to anoptical axis of the light source; wherein the first light output ismodulated as the first light source, retroreflector module, and quarterwaveplate move in rotary oscillation.
 3. The display of claim 2, furthercomprising a transparent assistant display positioned between the firstvisible real image and the first beam splitter module
 4. The display ofclaim 2, wherein the retroreflector module comprises one of a cat's eyeretroreflector array and a dihedral corner reflecting array.
 5. Thedisplay of claim 4, wherein the retroreflector module further comprisesa microlens array that increases focusing performance of theretroreflector module; wherein the microlens array comprises structuresperpendicular to the retroreflector module that block errantreflections.
 6. The display of claim 5, wherein the light source is anarray of light emitting diodes.
 7. The display of claim 1, wherein thefirst light source, retroreflector module, and quarter waveplate move intranslational oscillation in a direction perpendicular to an opticalaxis of the light source; wherein the first light output is modulated asthe first light source, retroreflector module, and quarter waveplatemove in translational oscillation.
 8. The display of claim 7, furthercomprising a transparent assistant display positioned between the firstvisible real image and the first beam splitter module.
 9. The display ofclaim 7, wherein the retroreflector module comprises one of a cat's eyeretroreflector array and a dihedral corner reflecting array.
 10. Thedisplay of claim 9, wherein the retroreflector module further comprisesa microlens array that increases focusing performance of theretroreflector module; wherein the microlens array comprises structuresperpendicular to the retroreflector module that block errantreflections.
 11. The display of claim 10, wherein the light source is anarray of light emitting diodes.
 12. The display of claim 1, wherein thefirst light source, retroreflector module, and quarter waveplate move incontinuous rotation around an axis perpendicular to an optical axis ofthe light source; wherein the first light output is modulated as thefirst light source, retroreflector module, and quarter waveplate move incontinuous rotation.
 13. The display of claim 12, further comprising atransparent assistant display positioned between the first visible realimage and the first beam splitter module
 14. The display of claim 12,wherein the retroreflector module comprises one of a cat's eyeretroreflector array and a dihedral corner reflecting array.
 15. Thedisplay of claim 14, wherein the retroreflector module further comprisesa microlens array that increases focusing performance of theretroreflector module; wherein the microlens array comprises structuresperpendicular to the retroreflector module that block errantreflections.
 16. The display of claim 15, wherein the light source is anarray of light emitting diodes.
 17. A persistent image retroreflectingdisplay comprising: a first light source that generates a first lightoutput; a first beam splitter module; and a retroreflector moduleoriented at ninety degrees relative to the first light source; whereinthe first light source transmits the first light output to the firstbeam splitter module; wherein the first beam splitter module splits thefirst light output into a first reflected component and a secondtransmitted component of the first light output; wherein the first beamsplitter module reflects the first reflected component to theretroreflector module; wherein the retroreflector module retroreflectsthe first reflected component back to the first beam splitter module;wherein the first beam splitter module splits the first reflectedcomponent into a third reflected component and a fourth transmittedcomponent; wherein the fourth transmitted component converges to a firstvisible real image in free space.
 18. The display of claim 17, whereinthe first light source and retroreflector module move in rotaryoscillation in a direction perpendicular to an optical axis of thefourth transmitted component; wherein the first light output ismodulated as the first light source and retroreflector module move inrotary oscillation.
 19. The display of claim 17, wherein the first lightsource and retroreflector module move in rotary oscillation in adirection perpendicular to an optical axis of the fourth transmittedcomponent; wherein the first light output is modulated as the firstlight source and retroreflector module move in translationaloscillation.
 20. The display of claim 17, wherein the first light sourceand retroreflector module move in continuous rotation around an axisperpendicular to an optical axis of the fourth transmitted component;wherein the first light output is modulated as the first light sourceand retroreflector module move in continuous rotation.